Optical Proximity Sensor Offset Compensation
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Solution Overview
Problem
Optical proximity sensors face challenges in minimizing light leakage and specular reflections, which reduce their ability to detect proximity accurately, due to the complexity, cost, and imperfections of light barriers, as well as interference from ambient light.
Innovation Solution
The implementation of an analog offset compensation method, where an offset current is combined with the detection signal to eliminate interference light, allowing for increased dynamic range and detection range without the need for a light barrier, and the use of an ADC with ADA feedback to reject ambient light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a light barrier is used to isolate the light source from the light detector, then light leakage is reduced, but device complexity, cost and size increase
Solution Approach 1:
The patent removes the light barrier component entirely and replaces it with an offset compensation method that uses electronic signal processing to eliminate the effects of direct light transmission, thereby reducing device complexity while maintaining the ability to prevent light leakage interference
Solution Approach 2:
The patent replaces the mechanical light barrier with an electronic offset compensation mechanism that subtracts the direct light signal from the detected signal, eliminating the need for physical isolation structures
2Object-affected harmful factors
If a light barrier is used to isolate the light source from the light detector, then light leakage is reduced, but cost increases
Solution Approach 1:
The patent eliminates the light barrier component, thereby reducing manufacturing cost, while implementing an offset compensation algorithm that achieves the same functional goal of preventing light leakage interference through electronic processing
Solution Approach 2:
The patent replaces expensive physical light barrier structures with a cost-effective software-based offset compensation method that achieves equivalent performance at lower manufacturing cost
3Object-affected harmful factors
If a light barrier is used to isolate the light source from the light detector, then light leakage is reduced, but detection range is limited
Solution Approach 1:
The patent replaces the light barrier with an electronic offset compensation system that can dynamically adjust and subtract direct light signals, enabling extended detection range while maintaining effective light leakage rejection through signal processing
4Strength
If the optical sensor is placed behind a cover plate, then protection is provided, but specular reflections increase
Solution Approach 1:
The patent replaces physical modifications to the cover plate with an electronic offset compensation method that identifies and subtracts specular reflection signals from the detected signal, maintaining cover plate protection while eliminating reflection interference
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the dynamic range and detection range of optical proximity sensors, reducing the impact of interference light and ambient light, thereby improving the accuracy and range of proximity detection.
Implementation Method 1
the magnitude of light originating from the light source that is reflected from an object and detected by the light detector
Implementation Method 2
an opaque light barrier is typically used to isolate the light source from the light detector
Implementation Method 3
the cover plate can be the glass covering a screen of a mobile phone, portable music player or personal data assistant (PDA), or the plastic covering a screen of a laptop, netbook or tablet computer
Implementation Method 4
When such a cover plate is placed over an optical sensor, the optical sensor is often susceptible to specular reflections
Data Source
AI summary
An optical proximity sensor includes a driver, light detector and offset signal generator. The driver selectively drives a light source. The light detector produces an analog detection signal indicative of an intensity of light detected by the light detector. The detected light can include light transmitted by the light source that reflected off an object within the sense region of the optical sensor, interference light and ambient light. The interference light includes light transmitted by the light source, and detected by the light detector, that was not reflected off an object within the sense region of the optical sensor. The offset signal generator selectively produces an analog offset signal that is combined with the analog detection signal produced by the photodetector to produce an analog compensated detection signal. The analog offset signal compensates for at least a portion of the interference light included in the light detected by the photodetector.